Technical Field
The present invention relates to a technology for selecting a vehicle (preceding vehicle) that is traveling ahead of an own vehicle.
Related Art
As a technology for reducing operating load placed on a driver who is driving a vehicle, an inter-vehicle control apparatus is known. The inter-vehicle control apparatus detects a vehicle (preceding vehicle) that is traveling ahead of the own vehicle. The inter-vehicle control apparatus controls the vehicle speed and the like to maintain a certain distance between the own vehicle and the preceding vehicle, enabling the own vehicle to automatically track the preceding vehicle.
In this type of apparatus, an estimated curve radius of the road on which the own vehicle is traveling is determined based on the yaw rate and vehicle speed of the own vehicle. In addition, a radar apparatus or the like is used to detect the position of the vehicle that is present ahead of the own vehicle. Based on the estimated curve radius and the position of the preceding vehicle, an own vehicle lane probability is determined for each detected preceding vehicle. The own vehicle lane probability indicates the probability of the vehicle being present in the same lane as the estimated traveling road of the own vehicle. Selection of a preceding vehicle and cancellation of the selection are performed based on the own vehicle lane probability.
However, because the detection values of the yaw rate vary, the calculation results for the estimated curve radius also vary. Therefore, to suppress the effects caused by the variation, a filter calculation is performed on the own vehicle lane probability.
Furthermore, at close distances, it is preferable that the filter be weak to ensure responsiveness, so that responses can be quickly made regarding merging vehicles and the like. However, at long distances, error in the estimated traveling road determined based on the estimated curve radius increases. When the value of the own vehicle lane probability significantly changes in accompaniment, a phenomenon occurs in which the preceding vehicle is frequently set and canceled. Therefore, it is preferable that the filter be strong to ensure stability of the own vehicle lane probability. As a result, a filter coefficient is also changed depending on the inter-vehicle distance (refer to, for example, JP-B-3427815).
However, whether the driver senses the inter-vehicle distance to be long or short differs depending on the vehicle speed. Therefore, in the conventional method of changing the filter characteristics based on the inter-vehicle distance, a problem occurs in that suitable filter characteristics cannot be actualized at every vehicle speed.
In other words, when the filter is set so as to become stronger near the inter-vehicle distance of 80 m, this setting is suited to the senses of the driver during low-speed cruising. However, the timing at which the filter strengthens is too early during high-speed cruising. Therefore, the driver senses that detection of a merging vehicle, for which responsiveness is required, becomes slow during high-speed cruising.